Browsing by Subject "Permeability"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Development of a Bed Permeability Test for Iron Ore Sintering
    (University of Minnesota Duluth, 2012) Englund, David J
  • Thumbnail Image
    Item
    Mechanical Properties of High Strength Concrete
    (Minnesota Department of Transportation, 1998-01) Mokhtarzadeh, Alireza; French, Catherine E.
    Researchers conducted an experimental program to investigate production techniques and mechanical properties of high-strength concrete and to provide recommendations for using these concretes in manufacturing precast/prestressed bridge girders. High-strength concretes with 28-day compressive strengths in the range of 8,000 to 18,600 psi (55.2 to 128 MPa) were produced. Test variables included total amount and composition ofcementitious material, portland cement, fly ash, and silica fume; type and brand of cement; type of silica fume, dry densified and slurry; type and brand of high-range water-reducing admixture; type of aggregate; aggregate gradation; maximum aggregate size; and curing. Testing determined the effects of these variables on changes in compressive strength and modulus of elasticity over time, on splitting tensile strength, on modulus of rupture, on creep, on shrinkage, and on adsorption potential as an indirect indicator of permeability. The study also investigated the effects of test parameters such as mold size, mold material, and end condition. More than 6,300 specimens were cast from approximately 140 mixes over a period of three years.
  • Thumbnail Image
    Item
    Nanoemulsion-like Polymersomes for Nanoreactors
    (2015-07) So, Soonyong
    Self-assembly of block copolymers in various selective solvents provides a means to control nanostructures. Among selective solvents, ionic liquids (ILs) are of great interest as reaction media, with the possibility of replacing organic solvents. However, the implementation ILs is limited by their high viscosity and cost. Phase transfer of IL-filled polymer vesicles (polymersomes) from the IL phase to water produces a very stable kind of "nanoemulsion"�. Nanoemulsion-like polymersomes have great potential as they confine a catalyst within the interiors, thus mitigating the mass transfer limitations of ILs while simultaneously providing a facile route to quantitative catalyst recovery The issues in the nanoreactor system and the mechanism of the phase transfer in the biphasic system are discussed. First, a new reversible reaction process with the thermo-responsive shuttling of the IL-filled polymersomes between the phases was designed. In nanoreactor applications, a narrowly distributed, small vesicle size is required. The size of polymersomes having rubbery and glassy membranes was controlled through mechanical and kinetic approaches. In the mechanical approach, the extrusion method was employed. For the kinetic approach, the amount of co-solvent and the hydrophilic fraction of amphiphilic block copolymer were varied and its effects on the size and dispersity were studied. Transport phenomena across the glassy and rubbery bilayer membranes was elucidated by NMR techniques to quantify the mobility inside and outside the polymersomes, plus the rate of exchange through the membrane. The dependence of the membrane thickness, glass transition temperature of the membranes and the partition coefficient of tracer molecules in the IL/water were also examined. We demonstrated a general boundary for the phase transfer of polymersomes in terms of a reduced tethering density for poly(ethylene oxide) (PEO), and analyzed the phenomena thermodynamically. The tethering density can be increased by increasing the block length of PEO and the size of the polymersomes, and the increased tethering density induces the phase transfer. Interfacial tension-related phase transfer led to develop a novel separation method in the biphasic system of the IL and water. By controlling the interfacial tension between the hydrophobic membrane and water, worm-like micelles and polymersomes were successfully separated.